Abstract

We examine the mobility reduction measured in hafnium-based dielectrics in n- and p-MOSFETs by means of extensive comparison between accurate multi-subband Monte Carlo simulations and experimental data for reasonably mature process technologies. We have considered scattering with remote (soft-optical) phonons and remote Coulomb interaction with single layers and dipole charges. A careful examination of model assumptions and limitations leads us to the conclusion that soft optical phononscattering cannot quantitatively explain by itself the experimental mobility reduction reported by several groups for neither the electron nor the hole inversion layers. Experimental data can be reproduced only assuming consistently large concentrations of Coulomb scattering centers in the gate stack. However, the corresponding charge or dipole density would result in a large threshold voltage shift not observed in the experiments. We thus conclude that the main mechanisms responsible for the mobility reduction in MOSFETs featuring Hafnium-based high-dielectric have not been completely identified yet. Additional physical mechanisms that could reconcile simulations with experimental results are suggested and critically discussed.

Received 29 December 2011Accepted 27 June 2012Published online 01 August 2012

Acknowledgments:

Work partially funded by the UE through the E.C. project GRAND (Grant Agreement 215752) and ENIAC.JTI-MODERN via the IUNET consortium. The authors would like to thank S. Monfray (ST Microelectronics, Crolles), C. Fenouillet-Beranger, and M. Cassé (CEA-LETI) for providing the devices in Fig. 10 and the experimental data in Fig. 11. They would like to thank also C. P. Rossel (IBM, Zurich) for making available the data of Ref. 48 in Fig. 8. We would like to thank P. K. Hurley and S. Monaghan (Tyndall National Institute) for providing us the experimental data in Fig. 7. Helpful discussions with J. Schmitz (University of Twente) and O. Engstrom (Chalmers and Warsaw University) are gratefully acknowledged.